User blog comment:GED4002/A question i dont see answered very often/@comment-27248965-20180114164512

The "6" icon means that the Pokémon was once under Pokémon Omega Ruby and Alpha Sapphire settings. This only appears on Pokémon caught before Port Decca update, because from that update onwards, all Pokémon PBB have been updated to be on-par with Pokémon Sun and Moon learnsets. This icon is only a flag for Developers, it has no use for us right now.